Why on earth would there be a dip precisely at 8k with both smaller and larger block sizes being faster?? -- Greg On 27 May 2009, at 03:51, Mark Wong <markwkm@gmail.com> wrote: > Hi all, > > A long long time ago (in 2004) I ran a series of tests surveying the > results of changing BLCKSZ when it was used for both the WAL logs and > the rest of the database system: > > http://archives.postgresql.org/pgsql-hackers/2004-03/msg01194.php > > Now more than 5 years later and now being able to set the WAL log and > the rest of the database to different block sizes, I have a set of > test results with DBT-2 showing the effects of changing the WAL log > block size on OLTP transaction throughput on ext2, ranging from 1KB to > 64KB: > > BS notpm % Change from default > -- ----- ---------- > 1 14673 -4.8% > 2 15864 2.9% > 4 15774 2.3% > 8 15413 (default) > 16 16118 4.6% > 32 16051 4.1% > 64 14874 -3.5% > > Pointers to raw data: > > BS url > -- --- > 1 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.1/ > 2 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.2/ > 4 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.4/ > 8 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.2/ > 16 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.16/ > 32 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.32/ > 64 http://207.173.203.223/~markwkm/community6/dbt2/m1500-8.4beta2/m1500.8.4beta2.wal.64/ > > > It appears for this workload using a 16KB or 32KB gets more than 4% > throughput improvement, but some of that could be noise. Nothing > quite jaw dropping yet. It'll be interesting to see if the > combination of changing the table block size can further improve the > performance. It will probably be interesting to try different > filesystems and filesystem blocksizes too. > > Regards, > Mark Wong > > -- > Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) > To make changes to your subscription: > http://www.postgresql.org/mailpref/pgsql-hackers
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